1. Field of the Invention
The present invention relates to a method of producing a rubber wiper blade having excellent wiping ability, durability and productivity, and a rubber wipe blade produced by this method.
2. Description of the Related Art
A rubber wiper blade is generally swept across the glass surface of a vehicle to wipe off raindrops or the like on the windshield. Therefore, rubber wiper blades having low frictional resistance and improved abrasion resistance are desired.
Since a rubber wiper blade is disposed on the outside of a vehicle, it is also necessary that it have resistance to the ozone and weather.
FIG. 6 is a perspective view of a conventional rubber wiper blade. In FIG. 6, the reference numeral 1 represents a rubber wiper blade, and reference numeral 2 is a base end portion which engages a holding fixture (not shown). The reference numeral 3 represents a neck portion; reference numeral 4 is a rocking portion; reference numeral 5 is a lip portion, and reference number 5a is the edge thereof.
Rubber wiper blade 1 is a molded product in which natural rubber or synthetic rubber is used. For a rubber wiper blade having natural rubber as the base material, the frictional resistance is lowered and the abrasion resistance is improved by subjecting the surface of the rubber blade to a chlorination treatment or a fluorination treatment, or by forming a coating layer 6 on the surface, as shown in FIG. 8.
In a rubber wiper blade containing synthetic rubber, such as ethylene propylene rubber (EPDM) as the base material, although the weathering resistance is excellent, the effect of a chlorination treatment on the reduction of the frictional resistance cannot be expected, it is subjected to a fluorination treatment so as to lower the frictional resistance and improve the abrasive resistance.
In order to enhance the productivity of a rubber wiper blade, what is referred to as a tandem rubber wiper blade, such as that shown in FIG. 9, has been proposed. The tandem rubber blade 7 shown in FIG. 9 is composed of two rubber wiper blades 1 united with each other at the lip portions 5. The surface of a common lip portion 8 of the tandem rubber wiper blade 7 is subjected to a coating treatment such as described above so as to provide a coating film.
The common lip portion 8 of the tandem rubber wiper blade 7 which is subjected to the coating treatment, is mounted on a bearer 9, and the tandem rubber wiper blade 7 is separated into two rubber wiper blades 1 by pressing a long knife blade 10 against the center portion of the common lip portion 8, as shown in FIG. 10. Such a treatment is referred to as a "before-cutting-coating treatment".
In contrast, in what is referred to as an "after-cutting-coating treatment", the common lip portion 8 of the tandem rubber wiper blade 7, which has not been subjected to a coating treatment, is mounted on the bearer 9, and the tandem rubber wiper blade 7 is separated into two rubber wiper blades 1 by pressing the long knife blade 10 against the center portion of the common lip portion 8. After the cutting step, the surface of the lip portion 5 of each rubber wiper blade 1 is subjected to a coating treatment; that is, for example, a coating material is sprayed onto the surface.
There are, however, some problems with the conventional rubber wiper blades, and with the conventional method of producing a rubber wiper blade. In particular, in the before-cutting-coating treatment, since the coating film 6 is hard, it is impossible to cut the common lip portion 8 with the knife blade 10 at a high speed and the edge of the knife 10 is abraded at the cutting step.
On the other hand, in the after-cutting-coating treatment, since the coating film 6 is also formed on the end portion of the lip portion 5, as shown in FIG. 8, the wiping ability of the rubber wiper blade 1 is deteriorated.